...are there any? I was wondering if any have been experimented with. They may produce less thrust but with perhaps enough weight loss (of the entire craft not just the engines) they would be feasible. Perhaps they could produce as much thrust as there metal counter parts. Who knows?

You have rockets which use graphite chambers and nozzles. A sort of carbon-carbon.

The problem with trying to use a conventional composite is in finding matrix material, the resin, that take the temperatures and erosion of not only the noisy part of the engine, but also the ancillaries like turbo-pumps etc. Its still cheaper, easier, and good-enough to use alloys.

For low cost liquid engines meant to only last one firing, there have been a few engines with ablative liners and carbon fiber overwrap to hold the pressure. Garvey and Protoflight both fired such engines.

Could a virtual nozzle be made? By either ionization or another means could two neutral fuel products combine and then be repelled by the surface of the rocket? I know this could be light if the ionization energy could be beamed in, from something not carried by the rocket. Also what about active cooling elements designed to be eventually replaced? Extracting work from lost heat and adding it back to thrust is like having more fuel....

_________________Let not the bindings of society hold you back from improving it.... the masses follow where the bold explore.

Could a virtual nozzle be made? By either ionization or another means could two neutral fuel products combine and then be repelled by the surface of the rocket? I know this could be light if the ionization energy could be beamed in, from something not carried by the rocket. Also what about active cooling elements designed to be eventually replaced? Extracting work from lost heat and adding it back to thrust is like having more fuel....

Yes, this has been proposed. Do a web search on "magnetic nozzle".

Bob Clark

_________________Nanotechnology now can produce the space elevator and private orbital launchers. It now also makes possible the long desired 'flying cars'. This crowdfunding campaign is to prove it:

...are there any? I was wondering if any have been experimented with. They may produce less thrust but with perhaps enough weight loss (of the entire craft not just the engines) they would be feasible. Perhaps they could produce as much thrust as there metal counter parts. Who knows?

Not exactly composites but fits in with your idea of using lightweight materials other than metals to reduce the weight of engines:

Part of the Integrated High PayoffRocket Propulsion Technology (IHPRPT) program, the efforts of the directorate include:1.Developing continuous fiber reinforced ceramic matrixcomposites (CMCs) for actively cooled thrust chambers andnozzles2.Demonstrating the feasibility of a transpiration-cooled thrustchamber3. Evaluating ceramic matrix composites for radiation coolednozzles.The goal is to develop and demonstrate these new technologiesso that they may be incorporated into future rocketengines. Using lightweight ceramics has the potential to reducethe weight of the combustion devices by up to 50%....Table 1 lists the materials and type of construction ofnumerous combustion devices, both historical and current. Asthe table shows, the materials of choice (for all the engine manufacturers)for combustion devices in large liquid fueled rocketengines have historically been stainless steels, nickel-basedsuperalloys, and copper alloys. These materials are selected fortheir high strength and high thermal conductivity in orderto cope with the stresses and extreme thermal environmentsof rocket engines. Since these alloys also have high densities(8-9 g/cm3), widespread reliance on them has traditionallyresulted in heavy engines.Designers would like to reduce the weight of rocketengines. A key performance criterion for engines is thrust-to-weightratio. Lighter engines and launch vehicles would allowheavier payloads to be placed into orbit at a lower cost. Onepath to lighter weight engines is replacement of conventionalhigh-density engine alloys with lightweight, high specificstrength ceramic composites. Two attractive candidates forthis application are carbon fiber reinforced silicon carbide(C/SiC) and silicon carbide fiber reinforced silicon carbide(SiC/SiC). These materials have low densities (2.0-2.4 g/cm3)and high strengths that they maintain to relatively high temperatures(2400-3000°F).http://ammtiac.alionscience.com/pdf/AMPQ8_1ART06.pdf

_________________Nanotechnology now can produce the space elevator and private orbital launchers. It now also makes possible the long desired 'flying cars'. This crowdfunding campaign is to prove it:

Cool I didn't know alot of this. I believe to get into orbit cheaply weight reduction is critical including the engines. I wonder the what the weight comparison of todays rockets of simular capacity is to rockets during the Apollo missions (sans fule of course).

Also I do like the first stage aircraft lifted idea. I knows it's not really a single stage operation but I like the 30% reduction in fuel by simply launching about ten miles up.

I'd like to look into Vacuum Carbon, or Silicon deposition to make a diamond/silicate substrate. If you burn Silane, or Methane in a vacuum, the elements deposit at the base in molecular layers, which you can reinforce with your high temperature fibers. Graphite is fairly thermostable, but not at the tempratures typical of a chemical rocket's exhaust. So, the substrate would have to be thermaly resistive enough to insulate the fiber as well. Diamond would also have to be designed not to harmonically shatter from the vibration of the exhaust, so I'd go for Silicate.

_________________"You can't have everything, where would you put it?" -Steven Wright.

Assuming we're talking about the Nozzle, or ventury here (There's a lot more to a liquid fueled rocket, and most of those parts could also be made from various composites.) The properties you're looking for are thermal stability, tensile strength, and then light weight. It doesn't matter how light it is, if it burns up, or shatters when you fire it. This is why most modern rockets pump cryogenic fuel in spiral tubes around the reaction surface. It pre-heats the fuel, and cools the nozzle so it doesn't melt. This requires a thermally conductive material, like alluminum, usually an alloy.

I know "Thermionic" is your new buzzword, and peizoelectric sounds pretty cool too, but Diamond, and Quartz (the most readilly availible Peizoelectric crystal) are less than ideal for a few reasons. First of all, these venturi are large, like cut a door in the side and live in them sized. (For Surface-Orbit launchers) We don't have the technology to make precision crystals on that scale, it would require a pressure kiln big enough to rent out as low income housing, and measument/themal control orders of magnitude more precise, and responsive to prevent flaws. That, and they tend to shatter when overstressed, because while they have high surface hardness, they're also brittle, with next to no tensile strength. Thermal expansion is also an issue, as they go from room temperature to vaporize your bones hot in fractions of a second, not to mention having all the pressure, and concussive vibration of containing half a steady state explosion.

Now, these pretty much run off of heat and pressure. Simplifying a lot here, but the chemical reactions (Hydrating oxygen, and tribonding N2) creates heat, which expands the gasses, which create pressure pressing up on the nozzle, and down on the atmosphere to make the rocket go thataway. Drawing off heat, thermionically, or otherwize basically pulls energy out of the system, making it less efficient. The heat-exchanger from pumping fuel into the nozzle raises efficiency by recycling that heat directly back into the chamber, and nozzle. Whatever you would use that energy for, it'd serve you a lot better for the job at hand, namely getting you to orbit in the first place.

_________________"You can't have everything, where would you put it?" -Steven Wright.

The idea is to use the thermionics to produce electricity, from heat, to cool the components that need it, and then that electricity could power other performance boosting components, like the ion rocket engines that have been researched lately, if I can take something that needs cooling and use it to fix another problem with it......

Thermionic diamond substrate and Piezoelectric substrates could be grown on a surface of another material. A laminate weave of a thin layer of each as well as a tensile layer could absorb both excessive heat and turbulance, and then redirect it into exaust acceleration then I can have a rocket that is lighter, reusable and more powerfull,... and safer, you could also control the heat in the ignition chamber walls, making them much more durable.

Another thought is upon re-entry the system could cool the ship and produce power for landing.

_________________Let not the bindings of society hold you back from improving it.... the masses follow where the bold explore.